This invention relates to improved methods for producing a dried particulate coal fuel having a reduced tendency to spontaneously ignite. More particularly, dried coal is sprayed with a special high flash point virgin vacuum reduced crude having a characterization factor above 10.8 and a 5% point in excess of 900.degree. F.
In many instances, coal as mined contains undesirably high quantities of water for transportation and use as a fuel. This problem is common to all coals although it is less severe in high grade coals, such as anthracite and bituminous coals. Attempts to dry crushed mined coals before shipment or storage have been inhibited by the tendency of such coals after drying to undergo spontaneous ignition and combustion in storage, transit or the like. As a result, a continuing effort has been directed to the development of improved methods whereby coals, especially low grade coals, such as sub-bituminous, lignite, and brown coals can be more than merely surface dried and thereafter safely transported, stored, and used as fuels.
In this regard, it has been previoulsy proposed to spray dried coal with hydrocarbons; but such oils are unsuitable for several reasons. For example, U.S. Pat. No. 4,201,657 proposes a blend of nonvirgin aromatic and asphalt hydrocarbons having a characterization factor no higher than 10.5 and preferably about 10.1 and a relatively low flash point and five percent point.